Cholinergic-opioidergic interaction in the central amygdala induces antinociception in the guinea pig

Autor(es)

C.R.A. Leite-Panissi ^[1] ; M.R. Brentegani ^[2] ; L. Menescal-de-Oliveira ^[3]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Faculdade de Odontologia de Ribeirão Preto. Departamento de Morfologia, Estomatologia e Fisiologia - Brasil

^[2] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

^[3] Universidade de São Paulo. Faculdade de Medicina de Ribeirão Preto. Departamento de Fisiologia - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 37, n. 10, p. 1571-1579, 2004-10-00.

Resumo

Several studies have demonstrated the involvement of the central nucleus of the amygdala (CEA) in the modulation of defensive behavior and in antinociceptive regulation. In a previous study, we demonstrated the existence of a cholinergic-opioidergic interaction in the CEA, modulating the defensive response of tonic immobility in guinea pigs. In the present study, we investigated a similar interaction in the CEA, but now involved in the regulation of the nociceptive response. Microinjection of carbachol (2.7 nmol) and morphine (2.2 nmol) into the CEA promoted antinociception up to 45 min after microinjection in guinea pigs as determined by a decrease in the vocalization index in the vocalization test. This test consists of the application of a peripheral noxious stimulus (electric shock into the subcutaneous region of the thigh) that provokes the emission of a vocalization response by the animal. Furthermore, the present results demonstrated that the antinociceptive effect of carbachol (2.7 nmol; N = 10) was blocked by previous administration of atropine (0.7 nmol; N = 7) or naloxone (1.3 nmol; N = 7) into the same site. In addition, the decrease in the vocalization index induced by the microinjection of morphine (2.2 nmol; N = 9) into the CEA was prevented by pretreatment with naloxone (1.3 nmol; N = 11). All sites of injection were confirmed by histology. These results indicate the involvement of the cholinergic and opioidergic systems of the CEA in the modulation of antinociception in guinea pigs. In addition, the present study suggests that cholinergic transmission may activate the release of endorphins/enkephalins from interneurons of the CEA, resulting in antinociception. (AU)

• Processo FAPESP: 97/14286-9 - Envolvimento do núcleo central da amígdala na modulação da imobilidade tônica, da antinocicepção e a participação da conexão funcional com a substância cinzenta periaquedutal em cobaias
• Beneficiário: Christie Ramos Andrade Leite Panissi
• Modalidade de apoio: Bolsas no Brasil - Doutorado